Electromagnetic switch



Jan. 26, 1960 K. KARRER 2,922,856

ELECTROMAGNETIC SWITCH Filed Dec. 20. 1956 2 Sheets-Sheet 1 l/II w wv m f Jan. 26, 1960 Filed Dec. 2o. 1956 K. KARRER ELECTROMAGNETIC SWITCH 2 Sheets-Sheet 2 United States Patent O s 2,922,856 ELECrRoMAGNE'rrC SWITCH Korbinian Karrer, Munich, Gern1any, assignor to Siemens & Halske Aktiengesellschaft Berlin and Munich, a corporation of Germanyv v Application December 20, 1956, Serial No. 629,541 11 claims. (Cl. 20o-87) This invention relates to electromagnetic switches and is particularly concerned with improvements in a magnetically operated switch of the general type as described in United States patent to W. B. Ellwood, No. 2,264,746, dated December 2, 1941.

The switch described in the above-noted patent comprises an evacuated or gas-filled tube containing two mutually spaced stationary positioned outer contact reeds or springs between which is disposed a third inner switchover spring. In its normal position, the switch-over spring is in contact-making engagement with one of the outer springs which is made of non-magnetic material. The other outer spring and the inner switch-over spring are both made of magnetizable material. Upon subjecting the corresponding switch structure -to the action of a magnetic field which is operative longitudinally thereof, lines of force will become active across the gap between the two magnetizable springs thus producing a force which draws the two springs together, thereby moving the inner switch-over spring from its normal position in contact engagement with one of the outer springs into contact-making engagement with the other outer spring. The spacing between the two outer springs is thereby maintained due to the provision of an insulating spacer member disposed therebetween. A contact arrangement of this kind is usually referred to as a breakmake contact arrangement, having a break side at which the contacts are normally closed and a make side at which the contacts are normally open, the contact closure at the make side being effected by the actuation of the switch-over spring from its break to its make position.

It happens frequently in this type of switch that the contact-making points stick together due to overloading or contact wear. If the sticking involves the contact points in the normal position, that is, at the break side, the excitation normally required for operation will not suliice for moving the inner switch-over spring to the alternate operated or make position. A considerably stronger excitation is therefore required for this purpose because the full range of the working gap has to be overcome to move the inner switch-over spring into its alternate make position. This gap remains due to the previously mentioned spacing member unaltered to the instant when the sticking at the break side is overcome at which instant the inner switch-over spring is displaced to move for contact closure to the make side.

The object of the invention is to reduce as far as possible the detrimental effect of the sticking of the contact points which generally cannot be altogether avoided. The invention overcomes this defect by positioning the outer contact spring related to the make side and provided for cooperation with the inner switch-over spring in the make or working position thereof, operatively and resiliently with respect to the other stationary outer spring provided for cooperation with the switching spring in the normal or break position thereof.

- The various objects and features of the invention will 2,922,856 Patented Jan. 26, 1960 appear from the description of embodiments which will be rendered below with reference to the accompanying drawings.

Referring to the drawings:

Figs. la to 1c show the arrangement of a break-make contact embodiment in various switching positions there` of; the contact-making end of the outer spring coacting' with the switch-over spring in the normal or break position thereof being made of non-magnetic material;

Fig. 2 illustrates a break-make contact embodiment wherein the entire outer spring at the break side is made of non-magnetic material;

Figs. 3a to 3c `indicate various switching positions of a simple break contact arrangement according to the invention; and

Figs. 4 to 6 show break-make contact arrangements according to the invention wherein the switch-over spring and the outer contact spring at the break side extend from one end of the contact envelope or tube inwardly thereof while the outer spring at the make side extends from the other end of the tube inwardly thereof.

Referring now to Figs. la to lc, Fig. la shows the contacts in the normal position. The tube may be a glass tube fused at its opposite ends as indicated at 1. Fused into one end of the tube are the two outer contact springs 2 and 3 and fused into the other end of the tube is therinner switch-over spring 4. The contactmaking end of the outer spring 3, which is relatively rigid, is made of non-magnetic material as indicated by the hatching thereof. The contact-making end of the yieldable inner switch-over spring 4 is disposed between the two outer springs 2 and 3, such end being normally in break contact-making engagement with the spring 3. The two contact springs 2 and 4 are made of magnetizable material.V

Upon subjecting the switch arrangement to a magnetic eld acting longitudinally thereof, lines of force will become operative across the gap between the springs 2 and 4 causing displacement of the spring 4 in the direction of spring 2, thus breaking the contact engagement between springs 3 and 4 (break side), shown in Fig. la, and closing contact between springs 4 and 2 (make side) as shown in Fig. lb. Upon cessation of the magnetic excitation, the contact spring 4 will flex back to initial position into normal break contact-making engagement with spring 3.

If sticking should occur between the springs 3 and 4, the gap between such springs will be reduced upon normal magnetic excitation due to radial inward flexing of the contact-making end of spring 2 as indicated in Fig. 1c, such spring being for this purpose operatively and resiliently positioned as noted before. The magnetic field now active across the reduced gap will suffice to effect operative actuation of the spring 4 to alternate make position.

It must be considered in this connection that the magnetic flux is inversely proportional to the magnetic impedance represented essentially by the working gap. The magnetic force is however directly proportional to the square of the flux. It follows, therefore, that the attractive force increases with the square of the reduction of the spacing between the corresponding springs.

The advantage of the switch arrangement according to the invention resides in the fact that, due to the resilience of the spring 2, the magnetic excitation required for the operation of the switch-over spring need not exceed normal excitation.

The spring 2 may be made stiffer than the spring 4 in order to secure actuation of the latter responsive to normal magnetic excitation.

It is understood, of course, that the entire spring 3 may be made of non-magnetic material as indicated in also be utilized in the case of-'a .simple break contact structure. avoid using the outercontact spring cooperatingwith the inner switching spring in the Working position. thereof as a spring'which is .operativein a circuit, or omitting a terminal therefor extending to the outside of the glass tube. y

A contact switch arrangement of thiskind isshown in Figs. 3a to 3c. This embodiment.correspondslargely to the embodiment illustrated inY Figs.. la to- 1c except that the spn'ng'Z has no terminal leading to theoutside, being held in position by a mounting member 5. The operation corresponds essentially to that describedain connection with Figs. la to lc. v Y

Figs. 4 to 6 show a break-make contact switch arrangement having the outer contact spring belonging to the break side and. also rthe switching spring7 extending from one end of the tube, while the Outercontact spring 8 cooperating with the switching: spring 7 in the actuated or make position-thereof extends from the otherend of the tube. Y

In the embodiment according to Fig. 4, all three'contact springs are made of magnetizable material. The outer break contact spring 6 cooperating with the inner switchover spring 7 in normal position thereof is xedly or rigidly disposed and slightly bent for 'contacting at its end ythe corresponding end of the switch-over spring 7, the latter being separated from the outer make contact springr8 by a gap. v

Upon energization of the switch'structureaccording to Fig. 4, a magnetic eld will become active across the gap between the inner ends of the springs 7 and 8, drawing these Vsprings together. The magnetic'force act-ive between theV ends -of the springs v6 and 7v is small' as compared with the force acting between the lends ofthe springs 7 and 8 due to the small overlap bet-WeenY springs 7 and 8 as compared with the considerably greater overlap'between springs 6 and 7 which causes a considerably greater inductance across the gap.

As in the previously described embodiments,V the outer contact spring 8 cooperating with the'inner switching spring 7, is arranged resiliently; accordingly, should sticking occur between the springs 6 and 7, the inner end of the contact spring 8 will be responsive toenergiza- Itis for Lthis purpose merely necessary to tion llex radially inwardly to reduce the gap, thereby causing the magnetic force to effect actuation of the spring 7. In the switch structure according to Fig. 4, the switching spring 7 is for flexibility thinner than the outer contact spring 6 disposed immediately adjacent thereto. The arrangement reduces the magnetic impedance on 'the corresponding side of the structure. It is for this reason possible to considerably weaken the switching spring 7 in the vicinity of its mounting because the flux `resulting in the contact actuation flows in part over the outer contact spring 6. The result is'that spring 7 can be shortened while fully preserving the ilexibility thereof. A shorter overall switchrmay in this manner be made. l y

An example of such a shorter'switch is shown in Fig. 5. The spring 7 is cross-sectionally reduced or' weakened immediately adjacent its fusion in the' tube end.

'In' the normal position, the contacting surfaces between the springs 6 and 7 are very'small, resulting upon energization in a certain undesired attraction of the parts due to corresponding magnetic induction. This eiect may be avoided by making the inner end of the spring 6 of nonmagnetic material `as indicated by the hatching appearing in Fig. 6.

Changes may be made within the scope 4and spirit of the'vappended claims.

I claim: n

1. In a magnetically operated switch structure having disposed within a sealed elongated tube a break-make con-5 tact spring arrangement including a rst outer contact spring related to the break side and a second outer contact spring related to the make side, and having a yieldable switch-over inner contactV spring operatively positioned between said rst and second outer contact springs and normally in contact-making engagement with said first outer contact spring related -to the break side, wherein breaking of the contact engagement between said inner Vspring and said rst outer spring may be' impeded by contact sticking; a device for reducing the effect kof such contact sticking so as to assure breaking the corresponding contact engagement, saidfdevice comprising operatively and resiliently positioning said second outer contact spring related to the maker side so as to cause such second outer contact spring, in caseef sticking ofsaid innerswitch-over springin contact engagement with-said rst outer contact spring, to tex, responsive to normal magnetic excitation, in the direction ofV said sticking inner Contact spring, thereby reducing the air gap between such second outer spring and saidfsticking inner spring and consequently etfectingincrease ofthe magneticattraction forces between these springs by an amount corresponding to the square of the reductionof the air gap, said increased magnetic attraction forces being'operative to actuate said inner switch-over contact spring and thereby' breaking the sticking contact engagement thereof with said rst outer contact spring. l

2. A device according tov claimy 1, wherein said second outer contact spring is relativelyfstiffer than said inner switch-over contact spring.

3. A device according to claim 1, wherein the contactmaking portion of said irst outer contact vspring is made of non-magnetizable material.

4. A device according to claim l,wherein the contactmaking portion of said second outer y,contact spring is made of magnetizable material.

5. VA device according to claim l, comprising a mounting member disposed upon said first outer contact spring for supporting Vsaid second outer contact spring.

6. A device according to claim 1, wherein said outer contact springs extend from one end of said tube inwardly thereof, and wherein said inner switch-over contact spring extends from the other end of said tube inwardly thereof.

7. A device according to claim 1, wherein said rst outer contact spring and said inner switch-over contact spring extend from one end of said tube inwardly thereof, and wherein said second outer contact spring extends from the other end of said tube inwardly thereof.

8. A device according to claim l, wherein said outer first and second contact springs and said inner switchover contact spring are made of magnetizable material.

9. A magnetically operated switch structure for reducing contact sticking, comprising two outer contact springs and a yieldable switch-over contact yspring operatively positioned between said outer contact springs and normally in engagement with one of the outer contact springs related to the resting side, the outer contact spring related to the working side of the contact making end ofthe contact spring being operatively and resiliently positioned with respect to the outer contact spring related to the resting side of the contact making end of the outer contact springs, the spring forces ofthe outer contact spring belonging to the working side being such that responsive to magnetic excitation in case of sticking of the switchover spring, with the outer contact spring related to the resting side, the air gap between said last mentioned outer contact spring and said switch-over' spring will be re'- duced upon' normal reenergization and the magnetic eld then active across the reduced gapr will effect operative actuation of the switch-over spring tothe alternate working position with an increase 'in' the operating. force because of the reduction of the aforesaid air gap, and said switch-over spring is reduced in cross-section contiguous to the mounting thereof for reducing the magnetic impedance on the adjacent side of the switch structure.

10. A magnetically operated switch structure for reducing contact sticking, comprising two outer contact springs and a yieldable switch-over contact spring operatively positioned between said outer contact springs and normally in engagement with one of the outer contact springs related to the resting side, the outer contact spring related to the working side of the contact making end of the contact spring being operatively and resiliently positioned with respect to the outer contact spring related to the resting side of the contact making end of the outer contact springs, the spring forces of the outer contact spring s belonging to the working side being such that responsive to magnetic excitation in case of sticking of the switchover spring, with the outer contact spring related to the resting side, the air gap between said last mentioned outer contact'spring and said switch-over spring will be reduced upon normal reenergization and the magnetic field then active across the reduced gap will effect operative actuation of the switch-over spring to the alternate Working position with an increase in the operating force because of the reduction of the aforesaid air gap, said switch-over spring is reduced in cross-section contiguous to the mounting thereof for reducing the magnetic impedance on the adjacent side of the switch structure, and further weakening the switch-over spring contiguous to the aforesaid mounting thereof since the magnetic flux resulting in the contact actuation flows in part over the contiguous outer contact spring permitting the shortening of said switch-over spring and said contiguous outer contact, whereby the length of the switch structure is shortened.

11. A magnetically operated switch structure for reducing contact sticking, comprising two outer contact springs and a yieldable switch-over contact spring operatively positioned between said outer contact springs and normally in engagement with one of the outer contact springs related to the resting side, the outer contact spring related to the working side of the contact making end of the contact spring being operatively and resiliently positionecl with respect to the outer contact spring related to the resting side of the Contact making end of the outer contact springs, the spring forces of the outer contact spring belonging to the working side being such that responsive to magnetic excitation in case of sticking ofthe switch-over spring, with the outer contact spring related to the resting side, the air gap between said last mentioned outer Contact spring and said switch-over spring will be reduced upon normal reenergization and the magnetic iieid then active across the reduced gap will effect operative actuation of the switch-over spring to the alternate working position with an increase in the operating force because of the reduction of the aforesaid air gap, said switch-over spring is reduced in cross-section contiguous to the mounting thereof for reducing the magnetic impedance on the adjacent side of the switch structure, further weakening the switch-over spring contiguous to the aforesaid mounting thereof since the magnetic flux resulting in the contact actuation flows in part over the contiguous outer contact spring permitting the shortening of said switch-over spring and said contiguous outer contact, whereby the length of the switch structure is shortened, and said inner end of the aforesaid last mentioned outer contact spring contiguous to the end of the switch-over spring being formed from non-magnetizable material, whereby in the normal position of the aforesaid outer contact spring and the switch-over spring, the undesirable attraction of said parts due to magnetic induction is avoided even though the contacting surface between said last mentioned springs is very small.

References Cited in the le of this patent UNITED STATES PATENTS 2,245,391 Dickten June 10, 1941 2,264,022 Ellwood Nov. 25, 1941 2,264,746 Ellwood Dec. 2, 1941 2,397,123 Brown Mar. 26, 1946 2,414,476 Mathes Jan. 21, 1947 2,481,003 Curtis Sept. 6, 1949 

